1. Field of the Invention
The invention relates to a medical guide wire used upon introducing a catheter into a cardiovascular system or the like.
2. Description of Prior Art
A medical guide wire, in the form of a flexible line wire, is disclosed in Japanese Provisional Publication No. 4-25024 to ensure a safety insertion for a catheter when inserting a balloon catheter into a blood vessel to treat a diseased area such as angiostenosis of the coronary artery or when inserting a thin flexible catheter into the blood vessel for an angiography.
Japanese Laid-open Patent Application No. 3-60674 discloses a medical guide wire in which a core shaft has a ball-like head portion to engage with an open end section of a catheter to prevent its forward movement. The ball-like head portion has an advantage that enables a manipulator to withdraw the guide wire together with the catheter.
As shown in FIG. 15, the medical guide wire 30 is in the form of a flexible thin line having a main wire portion 31, and inserted from its front distal portion 32 into a complicatedly twisted, turned or bifurcated blood vessel while pushing, pulling and turning a handling knob 33 placed outside a patient. This requires highly improved mechanical properties for the medical guide wire 30. It is especially indispensable for a front end portion 30A to have a high flexibility and restoring force enough to return back from the deformation because the front end portion 30A plays a leading part to introduce the medical guide wire 30 into the vascular tract. For this reason, a head plug 35 is fixed to a tip of a thin core line 34, and a front portion of a helical spring 36 is provided around the core line 34 to be soldered to the head plug 35. As an alternative, a molten solder attached to the core line 34 and the helical spring 36 to form the head plug 35 is presented as a main stream structure.
In the medical guide wire 30 in which the helical spring 36 is soldered to the head plug 35, a molten soldering material inevitably adheres to the helical spring 36 and clogs a clearance 37 between line element turns of the helical spring 36 due to dispersion and sputter caused from a capillary phenomenon of the molten soldering material during the soldering operation. For this reason, a rigid 30B portion appears to extend approximately by 1.5 mm from a top of the head plug 35 to a distal end of the helical spring 36 as shown at L5.
Meanwhile, upon inserting the medical guide wire 30 into a blood vessel 37 (FIG. 16) to introduce its leading portion 32 to a diseased area such as, for example, an angiostenosis area P, whether or not a manipulator should advance the leading portion 32 is judged after confirming that the leading portion 32 is normally inserted into a true lumen (intrinsic vascular tract lumen) safely enough to pierce the diseased area by visually confirming the leading portion 32 on a monitored image and a finger tip feeling information transmitted when a manipulator pushes, pulls and turns the handling knob 33. In this instance, the leading portion 32 transmits to the handling knob 33 that there is a difference in resistance between a central hard tissue of the angiostenosis area P and an inner wall of the normal intima 38 as the information of scratching and scraggy feelings. The feelings transmitted to the handling knob 33 is a clue formation to decide whether or not the leading portion 32 is normally in the true lumen to be further advanced.
In the prior structure, due to the extended rigid portion, the leading portion lacks a flexibility which fails to transmit an exact feeling information so that the leading portion 32 may be led astray into a false lumen by penetrating through the intima 38 to reach the media 39 of the vascular tract. Once led astray into the false lumen, the leading portion 32 has a danger of piercing through the adventitial coat 40 out of the vascular tract, and the manipulator will find it difficult to return the leading portion 32 back to the true lumen as well as to exlore a new route back to the true lumen. This becomes a great hindrance to treating and curing the diseased area particularly when considering the possibility that the false lumen is dilated.
Therefore, the present invention has made with the above drawbacks in mind, it is a main object of the invention to provide a medical guide wire which is capable of inserting a front distal portion normally into a true lumen without being led astray, thereby contributing to treating and curing a diseased area quickly with high precision.